Message Processors and Routers

1. Mule Integration Workshop
Message Processor or Routers

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3. Chapters
Schedule
Filter Types
Message Processor or Routers
Message Processor or Routers Types

4. Message Processor or Routers
Controls how events are sent and received by components in the
system.
Message Processors are used within flows to control how messages are
sent and received within that flow.
Message Processor Description
All Broadcast a message to multiple targets
Async Run a chain of message processors in a separate thread
Choice Send a message to the first matching message processor
Collection Aggregator Aggregate messages into a message collection
Collection Splitter Split a message that is a collection
Custom Aggregator A custom-written class that aggregates messages
Custom Processor A custom-written message processor
First Successful
Iterate through message processors until one succeeds (added
in 3.0.1)
Idempotent Message
Filter
Filter out duplicate message by message ID

5. Message Processors or Routers (Contd)
Message Processor Description
Idempotent Secure
Hash Message Filter
Filter out duplicate message by message content
Message Chunk
Aggregator
Aggregate messages into a single message
Message Chunk
Splitter
Split a message into fixed-size chunks
Message Filter Filter messages using a filter
Processor Chain Create a message chain from multiple targets
Recipient List Send a message to multiple endpoints
Request Reply
Receive a message for asynchronous processing and accept the asynchronous
response on a different channel
Resequencer Reorder a list of messages
Round Robin Round-robin among a list of message processors (added in 3.0.1)
Until Successful Repeatedly attempt to process a message until successful
Splitter Split a message using an expression
WireTap
Send a message to an extra message processor as well as to the next message
processor in the chain

6. All
All
 The All message processor can be used to send the same message to
multiple targets.
 If any of the targets specified is an endpoint that has a filter configured
on it, only messages accepted by that filter are sent to that endpoint.
 All messages (if any) returned by the targets are aggregated together and
form the response from this processor.
Eg:
<all>
<jms:endpoint queue="test.queue" transformer-refs="StringToJmsMessage"/>
<http:endpoint host="10.192.111.11" transformer-refs="StringToHttpClientRequest"/>
<tcp:endpoint host="10.192.111.12" transformer-refs="StringToByteArray"/>
</all>

7. Async
Async
 The Async message processor runs a chain of message processors in
another thread, optionally specifying a threading profile for the thread to
be used.
Eg:
<async>
<append-string-transformer message="-async" />
<vm:outbound-endpoint path="async-async-out" exchange-pattern="one-way" />
<threading-profile doThreading="true" maxThreadsActive="16"/>
</async>
This transforms the current message and sends it to the specified endpoint, using a threadpool
that contains up to 16 concurrent threads.

8. Choice
Choice
 The Choice message processor sends a message to the first message
processor that matches. If none match and a message processor has been
configured as "otherwise", the message is sent there. If none match and no
otherwise message processor has been configured, an exception is thrown.
Eg:
<choice>
<when expression="payload=='foo'" evaluator="groovy">
<append-string-transformer message=" Hello foo" />
</when>
<when expression="payload=='bar'" evaluator="groovy">
<append-string-transformer message=" Hello bar" />
</when>
<otherwise>
<append-string-transformer message=" Hello ?" />
</otherwise>
</choice>
If the message payload is "foo" or "bar", the corresponding transformer is run. If not, the transformer
specified under "otherwise" is run.

9. Collection Aggregator
 The Collection Aggregator groups incoming messages that have matching
group IDs before forwarding them.
 The group ID can come from the correlation ID or another property that
links messages together.
Eg:
<collection-aggregator timeout="6000" failOnTimeout="false"/>

10. Collection Splitter
 The Collection Splitter acts on messages whose payload is a Collection
type.
 It sends each member of the collection to the next message processor as
separate messages.
 Attribute “enableCorrelation” to determine whether a correlation ID is
set on each individual message.
Eg:
<collection-splitter enableCorrelation="IF_NOT_SET"/>

11. Custom Aggregator
 A Custom Aggregator is an instance of a user-written class that
aggregates messages. This class must implement the interface
MessageProcessor.
 Often, it will be useful for it to subclass AbstractAggregator, which
provides the skeleton of a thread-safe aggregator implementation,
requiring only specific correlation logic.
Eg:
<custom-aggregator failOnTimeout="true" class="com.mycompany.utils.PurchaseOrderAggregator"/>

12. First Successful
 The First Successful message processor iterates through its list of child message
processors, routing a received message to each of them in order until one processes
the message successfully. If none succeed, an exception is thrown.
 Success is defined as:
 If the child message processor thows an exception, this is a failure.
 Otherwise:
 If the child message processor returns a message that contains an exception payload, this
is a failure.
 If the child message processor returns a message that does not contain an exception
payload, this is a success.
 If the child message processor does not return a message (e.g. is a one-way endpoint),
this is a success.
Eg:
<first-successful>
<http:outbound-endpoint address="http://localhost:6090/weather-forecast" />
<http :outbound-endpoint address="http://localhost:6091/weather-forecast" />
<http:outbound-endpoint address="http://localhost:6092/weather-forecast" />
<vm:outbound-endpoint path="dead-letter-queue" />
</first-successful>

13. Idempotent Message Filter
 An idempotent filter checks the unique message ID of the incoming message
to ensure that only unique messages are received by the flow.
 The ID can be generated from the message using an expression defined in the
idExpression attribute. By default, the expression used is #[message:id], which
means the underlying endpoint must support unique message IDs for this to
work. Otherwise, a UniqueIdNotSupportedException is thrown.
Eg:
<idempotent-message-filter idExpression="#[message:id]-#[header:foo]">
<simple-text-file-store directory="./idempotent"/>
</idempotent-message-filter>
The optional idExpression attribute determines what should be used as the unique message ID. If this attribute
is not used, #[message:id] is used by default.

14. Idempotent Secure Hash Message Filter
 This filter calculates the hash of the message itself using a message digest
algorithm to ensure that only unique messages are received by the flow.
 This approach provides a value with an infinitesimally small chance of a
collision and can be used to filter message duplicates.
 The hash is calculated over the entire byte array representing the message, so
any leading or trailing spaces or extraneous bytes (like padding) can produce
different hash values for the same semantic message content.
 This router is useful when the message does not support unique identifiers.
Eg:
<idempotent-secure-hash-filter messageDigestAlgorithm="SHA26">
<simple-text-file-store directory="./idempotent"/>
</idempotent-secure-hash-message-filter>
Idempotent Secure Hash Message Filter also uses object stores, which are configured the same way as the
Idempotent Message Filter. The optional messageDigestAlgorithm attribute determines the hashing algorithm
that will be used. If this attribute is not specified, the default algorithm SHA-256 is used.

15. Message Chunk Aggregator
 After a splitter such as the Message Chunk Splitter splits a message into parts,
the message chunk aggregator router reassembles those parts back into a
single message.
 The aggregator uses the message's correlation ID to identify which parts
belong to the same message.
Eg:
<message-chunk-aggregator>
<expression-message-info-mapping messageIdExpression="#[header:id]"
correlationIdExpression="#[header:correlation]"/>
</message-chunk-aggregator>
The optional expression-message-info-mapping element allows you to identify the correlation ID in the message
using an expression. If this element is not specified, MuleMessage.getCorrelationId() is used. The Message Chunk
Aggregator also accepts the timeout and failOnTimeout attributes

16. Message Chunk Splitter
 The Message Chunk Splitter allows to split a single message into a number of
fixed-length messages that will all be sent to the same message processor.
 It will split the message up into a number of smaller chunks according to the
messageSize attribute that you configure for the router.
 The message is split by first converting it to a byte array and then splitting this
array into chunks.
 If the message cannot be converted into a byte array, a RoutingException is
raised.
Eg:
<message-chunk-splitter messageSize="512"/>

17. Message Filter
 The Message Filter is used to control whether a message is processed by
using a filter. In addition to the filter, we can configure whether to throw an
exception if the filter does not accept the message and an optional message
processor to send unaccepted messages to.
Eg:
<message-filter throwOnUnaccepted="false" onUnaccepted="rejectedMessageLogger">
<message-property-filter pattern="Content-Type=text/xml" caseSensitive="false"/>
</message-filter>

18. Processor Chain
 A Processor Chain is a linear chain of message processors which process a
message in order. A Processor Chain can be configured wherever a message
processor appears in a Mule Schema
Eg:
<wire-tap>
<processor-chain>
<append-string-transformer message="tap" />
<vm:outbound-endpoint path="wiretap-tap" exchange-pattern="one-way" />
</processor-chain>
</wire-tap>

19. Recipient List
 The Recipient List message processor allows to send a message to multiple
endpoints by specifying an expression that, when evaluated, provides the list
of endpoints.
 These messages can optionally be given a correlation ID, as in the Collection
Splitter
Eg:
<recipient-list enableCorrelation="ALWAYS" evaluator="header" expression="myRecipients"/>
which finds the list of endpoints in the message header named myRecipients.

20. Request Reply
 The Request Reply message processor receives a message on one channel,
allows the back-end process to be forked to invoke other flows
asynchronously, and accepts the asynchronous result on another channel.
Eg:
<flow name="main">
<vm:inbound-endpoint path="input"/>
<request-reply storePrefix="mainFlow">
<vm:outbound-endpoint path="request"/>
<vm:inbound-endpoint path="reply"/>
</request-reply>
<component class="com.mycompany.OrderProcessor"/>
</flow>
<flow name="handle-request-reply">
<vm:inbound-endpoint path="request"/>
<component class="come.mycompany.AsyncOrderGenerator"/>
</flow>
The request is received in the main flow and passed to the request-reply router, which
implicitly sets the MULE_REPLYTO message property to the URL of its inbound endpoint
(vm://reply) and asynchronously dispatches the message to the (one-way) vm://request
endpoint, where it is processed by the handle-request-reply flow.

21. Request Reply - Contd
The main flow then waits for a reply. The handle-request-reply flow passes the message to the
AsynchOrderGenerator component. When this processing is complete, the message is sent to vm://reply
(the value of the MULE_REPLYTO property.) The asynchronous reply is received and given to the OrderProcessor
component to complete the order processing.
In more advanced cases, you might not want the automatic forwarding of the second flow's
response to the request-reply inbound endpoint. For instance, the second flow might
trigger the running of a third flow, which then generates and sends the reply. In
these cases, you can remove the MULE_REPLYTO property with a Message Properties
Transformer:
<request-reply storePrefix="mainFlow">
<vm:outbound-endpoint path="request">
<message-properties-transformer scope="outbound">
<delete-message-property key="MULE_REPLYTO"/>
</message-properties-transformer?
</vm:outbound-endpoint>
<vm:inbound-endpoint path="reply"/>
</request-reply>

22. Resequencer
 The Resequencer sorts a set of received messages by their correlation
sequence property and issues them in the correct order. It uses the timeout
and failOnTimeout attributes to determine when all the messages in the set
have been received.
Eg:
<resequencer timeout="6000" failOnTimeout="false"/>

23. Round Robin
 The Round Robin message processor iterates through a list of child message
processors in round-robin fashion: the first message received is routed to the
first child, the second message to the second child, and so on. After a
message has been routed to each child, the next is routed to the first child
again, restarting the iteration.
Eg:
<round-robin>
<http:outbound-endpoint address="http://localhost:6090/weather-forecast" />
<http:outbound-endpoint address="http://localhost:6091/weather-forecast" />
<http:outbound-endpoint address="http://localhost:6092/weather-forecast" />
</round-robin>

24. Splitter
 A Splitter uses an expression to split a message into pieces, all of which are
then sent to the next message processor. Like other splitters, it can optionally
specify non-default locations within the message for the message ID and
correlation ID.
Eg:
<splitter evaluator="xpath" expression="//acme:Trade"/>
This uses the specified XPath expression to find a list of nodes in the current message and sends each of them as a
separate message.

25. Until Successful
 The Until Successful message processor processes a message with its child
message processor until the processing succeeds. This processing occurs
asynchronously, therefore execution is returned to the parent flow
immediately.
 The Until Successful message processor is able to retry:
 Dispatching to outbound endpoints, for example, when reaching out to a
remote web service that may have availability issues.
 Execution of a component method, for example, to retry an action on a
Spring Bean that may depend on unreliable resources.
 A sub-flow execution, to keep re-executing several actions until they all
succeed.
 Any other message processor execution, to allow more complex scenarios.
Eg:
<until-successful objectStore-ref="objectStore" maxRetries="5" secondsBetweenRetries="60">
<outbound-endpoint ref="retriableEndpoint" />
</until-successful> .

26. Until Successful (Contd)
 This message processor needs an ListableObjectStore instance in order to persist
messages pending (re)processing. There are several implementations available in
Mule, including the following:
 DefaultInMemoryObjectStore. The default in-memory store.
 DefaultPersistentObjectStore. The default persistent store
 FileObjectStore. A file-based store.
 QueuePersistenceObjectStore. The global queue store.
 SimpleMemoryObjectStore. An in-memory store
Eg:
<spring:bean id="objectStore" class="org.mule.util.store.SimpleMemoryObjectStore" />
 Success or failure are defined as:
 If the child message processor throws an exception, this is a failure.
 If the child message processor does not return a message (e.g. is a one-way
endpoint), this is a success.
 If a 'failure expression' has been configured, the return message is evaluated
against this expression to determine failure or not.

27. Until Successful (Contd)
 Otherwise:
 If the child message processor returns a message that contains an exception payload, this
is a failure.
 If the child message processor returns a message that does not contain an exception
payload, this is a success.
Eg: how to configure the failure expression
<until-successful objectStore-ref="objectStore"
failureExpression="#[header:INBOUND: http.status != 202]"
maxRetries="6"
secondsBetweenRetries="600">
<http:outbound-endpoint address="http://acme.com/api/flakey"
exchange-pattern="request-response"
method="POST"/>
</until-successful>

28. Until Successful (Contd)
 The Until Successful message processor is also able to synchronously
acknowledge that it has accepted a message and will try to process it
repeatedly.
Eg:
<until-successful objectStore-ref="objectStore" ackExpression="#[message:correlationId]"
maxRetries="3" secondsBetweenRetries="10">
<flow-ref name="signup-flow" />
</until-successful>

29. WireTap
 The WireTap message processor allows to route certain messages to a
different message processor as well as to the next one in the chain. For
instance, To copy all messages to a specific endpoint, configure it as an
outbound endpoint on the WireTap routing processor:
Eg:
<wire-tap>
<vm:outbound-endpoint path="tapped.channel"/>
</wire-tap>
Using Filters with the WireTap
 The WireTap routing processor is useful both with and without filtering. If
filtered, it can be used to record or take note of particular messages or to
copy only messages that require additional processing.

30. WireTap (Contd)
 If filters aren't used, can make a backup copy of all messages received. The
behavior here is similar to that of an interceptor, but interceptors can alter
the message flow by preventing the message from reaching the component.
WireTap routers cannot alter message flow but just copy on demand. In this
example, only messages that match the filter expression are copied to the vm
endpoint.
Eg:
<wire-tap>
<vm:outbound-endpoint path="tapped.channel"/>
<wildcard-filter pattern="the quick brown*"/>
</wire-tap>

31. Thank you